Table Of ContentUniversity of Tennessee, Knoxville
Trace: Tennessee Research and Creative
Exchange
Masters Teses Graduate School
12-2010
Te Efects of Living Mulches on Organic,
Reduced-Till Broccoli Growth and Management
Sarah Elizabeth Broughton
To the Graduate Council:
I am submiting herewith a thesis writen by Sarah Elizabeth Broughton entitled "Te Efects of Living
Mulches on Organic, Reduced-Till Broccoli Growth and Management." I have examined the fnal
electronic copy of this thesis for form and content and recommend that it be accepted in partial
fulfllment of the requirements for the degree of Master of Science, with a major in Plant Sciences.
Annete L. Wszelaki, Major Professor
We have read this thesis and recommend its acceptance:
Dennis Deyton, Gary Bates, Jerome Grant
Accepted for the Council:
Carolyn R. Hodges
Vice Provost and Dean of the Graduate School
(Original signatures are on fle with ofcial student records.)
To the Graduate Council:
I am submitting herewith a thesis written by Sarah Elizabeth Broughton entitled “The
Effects of Living Mulches on Organic, Reduced-Till Broccoli Growth and Management.”
I have examined the final electronic copy of this thesis for form and content and
recommend that it be accepted in partial fulfillment of the requirements for the degree of
Master of Science, with a major in Plant Sciences.
Annette Wszelaki, Major Professor
We have read this thesis
and recommend its acceptance:
Dennis Deyton
Gary Bates
Jerome Grant
Accepted for the Council:
Carolyn R. Hodges
Vice Provost and Dean of the Graduate School
(Original signatures are on file with official student records.)
The Effects of Living Mulches on Organic, Reduced-Till
Broccoli Growth and Management
A Thesis Presented for
the Master of Science
Degree
The University of Tennessee, Knoxville
Sarah Elizabeth Broughton
December 2010
Copyright © 2010 by Sarah E. Broughton
All rights reserved.
ii
Acknowledgements
Thank you to Dr. Annette Wszelaki for providing direction in the design and
implementation of this research project; to my research advisory committee, Dr. Dennis
Deyton, Dr. Gary Bates, Dr. Jerome Grant and Dr. Neal Eash, for sharing your expertise;
to Dr. Bobby Simpson, Lee Ellis, Billy Lively and Bobby Terry at the East Tennessee
Research and Education Center Organic Crops Unit for providing the land and
maintenance of my field plots. I would also like to thank my fellow students and co-
workers in the Organic and Sustainable Crop Production program; Mary Rogers, Bobby
Evans, Alexandra Spaulding, Alex Minderman, D.J. Mitchell, Grant McCarty and Jeff
Martin for their help.
iii
Abstract
Conservation tillage programs have been successfully implemented for many
agronomic cropping systems, but adoption of reduced tillage for vegetable crops has been
slow. As many conventionally managed conservation tillage programs rely on synthetic
herbicides for clean cultivation, alternative methods must be devised to suppress weed
pressure and reduce reliance on mechanical cultivation to aid in the development of
reduced tillage programs for organic cropping system. Strip tillage is a reduced tillage
method that is well suited to vegetable crop production, and the utilization of cover crops
and living mulches between rows provides a viable weed management option for organic
systems.
The adoption of reduced tillage and the inclusion of cover crops and living
mulches have the potential to alter the agroecosystem in ways that impact plant
development and crop yield, and augment weed, insect and disease pressure. The current
study focuses on the use of strip tillage and the interplanting of spring-seeded living
mulches and overwintered cover crops for early-season organic broccoli production.
Data were collected on ground cover provided by cover crops and living mulches, crop
physiological status (petiole sap nitrate, photosynthetic rate, plant growth and crop
biomass) and pest pressure (weed relative abundance, insect density and disease
incidence and severity).
Living mulches provided the greatest ground coverage when cover crop
establishment was poor; however, when cover crops produced a large amount of biomass,
living mulch establishment was suppressed. Decreases in herbivorous pests and
suppression of grassy and cool-season weed species were also observed, indicating that
strip tillage and the use of spring-seeded living mulches and overwintered cover crops
may provide beneficial pest management strategies. Decreases in crop growth and
biomass, and decreases in petiole sap nitrate were observed, however, indicating
reductions in crop vigor and yield may be expected with the implementation of strip
tillage and living mulch crops. It is suggested that the utilization of strip tillage and
living mulch crops may provide benefits to pest management which may outweigh
declines in yield.
iv
Table of Contents
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vi
List of Figures
Figure A.1 Adaptation zones and mean annual air temperature (°F) for cover crop species
utilized in the Southern US (Ball et al., 2002). ......................................................... 29
Figure B.1 Ground coverage from living mulches between tillage treatments in 2009.... 48
Figure B.2 Ground coverage among living mulch treatments in 2009 ............................. 49
Figure B.3 Tillage by living mulch interaction at the vegetative growth stage of broccoli
in 2009....................................................................................................................... 50
Figure B.4 Tillage by living mulch interaction at the buttoning growth stage of broccoli
in 2009....................................................................................................................... 51
Figure B.5 Total ground coverage for non-marketable crops among living mulch
treatments in 2009 ..................................................................................................... 52
Figure B.6 Ground coverage among living mulch treatments sampled at the buttoning
growth stage of broccoli in 2010............................................................................... 53
Figure B.7 Total ground coverage for non-marketable crops sampled at the buttoning
growth stage of broccoli in 2010............................................................................... 54
Figure C.1 Petiole sap nitrate concentration between tillage treatments at three broccoli
growth stages in 2010................................................................................................ 74
Figure C.2 Photosynthetic rate between tillage treatments at the pre-harvest growth stage
of broccoli in 2010 .................................................................................................... 75
Figure C.3 Plant height between tillage treatments at two broccoli growth stages in 2009
................................................................................................................................... 76
Figure C.4 Plant height among living mulch treatments at two broccoli growth stages in
2009........................................................................................................................... 77
Figure C.5 Plant height between tillage treatments at three broccoli growth stages in 2010
................................................................................................................................... 78
Figure C.6 Stalk diameter between tillage treatments at the pre-harvest growth stage of
broccoli in 2010......................................................................................................... 79
Figure C.7 Fresh and dry weights among living mulch treatments at the pre-harvest
growth stage of broccoli in 2009............................................................................... 80
Figure C.8 Fresh and dry weights between tillage treatments at the pre-harvest growth
stage of broccoli in 2010 ........................................................................................... 81
Figure D.1 Mean herbivore density for weekly samplings throughout the broccoli
production period within tillage and living mulch treatments in 2009 ................... 117
Figure D.2 Mean herbivore density for weekly samplings throughout the broccoli
production period within tillage and living mulch treatments in 2010 ................... 118
Figure D.3 Mean predator density for weekly samplings throughout the broccoli
production period within tillage and living mulch treatments in 2009 ................... 119
Figure D.4 Mean predator density for weekly samplings throughout the broccoli
production period within tillage and living mulch treatments in 2010 ................... 120
vii
